This application claims benefit of Japanese Application No. 2001-069104 filed on Mar. 12, 2001, and No. 2002-017315 filed on Jan. 25, 2002, the contents of which are incorporated by this reference.
1. Field of the Invention
The present invention relates to an endoscope and, more particularly, an autoclave sterilization type endoscope.
2. Description of the Related Art
Endoscopes are now widely used in the medical care field. The insert section of the endoscope is inserted into the body cavity of a human to observe a deep portion of the body, and if necessary, a medical treatment is performed using an instrument together with the endoscope.
To control communicable diseases, sterilizing and disinfecting a medical endoscope after use are an essential requirement.
Gaseous disinfectants, such as ethylene oxide, or antiseptic solutions are conventionally used in a sterilization process. As is well known, gaseous disinfectants are highly toxic, and a sterilization process becomes complex to assure safety of humans. Since aeration to evacuate gas residing on an instrument subsequent to the sterilization process takes time, the endoscope cannot be used immediately after the sterilization process. Furthermore, adverse effects of the gas to the environment become a concern. The running cost involved in the sterilization process is high.
The management of the antiseptic solutions is typically complicated, and a great deal of cost is required to dispose the used antiseptic solutions.
In the field of endoscopes, the autoclave sterilization is becoming a mainstream sterilization process because it requires no complex handling procedure, permits use immediately subsequent to the sterilization process, and involves no high running cost. The autoclave sterilization process sterilizes bacteria by infiltrating vapor into the bacteria under a high pressure (of about 0.2 MPa) and a high temperature (within a range of from 120xc2x0 C. to 135xc2x0 C.).
However, high-pressure vapor typically penetrates almost all polymeric materials (resin, rubber, resin adhesives, etc). For example, epoxy resin, which is a widely used adhesive agent, permits a high-pressure vapor to penetrate therethrough in the autoclave sterilization process. The epoxy resin under a direct attack by the high-pressure vapor deteriorates and may be cracked. Since the autoclave sterilization process involves a high temperature, a stress is generated between components due to difference in thermal expansion coefficient from material to material. This may be another cause of cracks in the adhesive agent.
In the autoclave sterilization process, vapor penetrates through a connection portion of an optical window, and enter a lens system, thereby clouding the surface of a lens in the lens system. There is a conventionally available technique which air-tight connects the connection portion of an optical window member by soldering or brazing rather than by using an adhesive.
For example, Japanese Unexamined Patent Application Publication No. 2000-342512 discloses a technique in which a lens barrel is subjected to a surface treatment such as gold plating before soldering a distal-end lens as the optical window member. To perform sound brazing, a surface treatment, such as gold plating, nickel plating, or tin plating, needs to be performed on the surface of a component. Such a pre-brazing surface finish is typically glossy. The surface of the lens barrel then becomes reflective. Since light rays are reflected from a flat bottom of a lens brazed to the lens barrel and an inner circumference of a lens barrel of a second lens thereafter, optical problems such as flare are created.
A metal such as brass permits sound brazing without the need for plating. If such a metal is used for the lens barrel, the material itself is glossy, and the same problem is created.
Japanese Unexamined Patent Application Publication No. 2000-107120 discloses a technique in which a lens barrel supporting a lens is fabricated of a ceramic such as aluminum nitride, sialon, alumina, silicon nitride, or silicon carbide. Since the surface of these materials is not sufficiently low in reflectance, the inner diameter of the lens barrel is increased so that no light rays are incident on the inner circumference of the lens barrel. Furthermore, when a ceramic is used for the lens barrel, the thickness of the lens barrel needs to be increased to assure machinability and mechanical strength. Consequently, the image pickup unit of the endoscope becomes bulky in size with an enlarged distal end diameter of the endoscope.
Japanese Unexamined Patent Application Publication No. 2000-107120 discloses a technique in which an optical diaphragm is not arranged immediately proximal to an optical window. In this arrangement, a light ray is reflected from a distal end of a metal-plated lens barrel supporting an optical window member, and is incident on a solid-state image pickup device, thereby resulting in optical problems. To control such optical reflections, the optical window and the distal end barrel need to be enlarged in diameter. A bulky image pickup unit thus results.
Accordingly, it is an object of the present invention to provide an endoscope with a small diameter distal end wherein the endoscope is free from clouding in a viewing optical system thereof and optical problems such as flare during an autoclave sterilization process.
An endoscope of the present invention in one aspect includes a viewing optical system including a plurality of optical members and an optical window member arranged at a distal end of the viewing optical system, a first lens barrel having a brazing surface in at least a brazing portion thereof, and supporting the optical window member brazed thereon, a second lens barrel arranged to be proximal with respect to the optical window member and supporting the optical member on the inner circumference thereof. At least a distal end surface of one of the second lens barrel, the diaphragm member, the spacer ring, and the optical member has light reflectance lower than that of the brazing surface of the first lens barrel.
An endoscope of the present invention in another aspect includes a viewing optical system including a plurality of optical members and an optical window member arranged at a distal end of the viewing optical system, a first lens barrel having a brazing surface in at least a brazing portion thereof, and supporting the optical window member brazed thereon, and a second lens barrel arranged to be proximal with respect to the optical window member and supporting the optical member on the inner circumference thereof, wherein at least the inner circumference of the second lens barrel has light reflectance lower than that of the brazing surface of the first lens barrel or has a reflection surface more irregular than the brazing surface of the first lens barrel.